Evaluation of the simplified generalised standard additions method for calibration in the direct analysis of solid samples by graphite furnace atomic spectrometric techniques

Abstract

In combining the principles of experimental design and the simplified approach to the generalised standard additions method, a useful calibration strategy is obtained for the single-component analysis of solid samples. By varying both the solid sample mass and the amount of analyte added, the observed response is defined by these two variables and may be geometrically described as a surface in three-dimensional space. The use of multiple regression techniques then allows the analyte concentration in the solid to be computed from the response plane. Simultaneous blank correction and quantification is also performed. The importance of a well designed experimental lay-out and the effects of random errors or noise on the accuracy of the procedure are investigated, and some analytical results are given. It is shown that the approximation of the analyte concentration obtained is fairly insensitive to curvature in the calibration function, but tends to be biased high in the presence of intense noise. This latter effect is a major limitation given the inhomogeneity of most solid samples which leads to irreproducible or “noisy” results.